Supayalat (Burmese: စုဖုရားလတ်, pronounced [sṵpʰəjá laʔ]; 13 December 1859 – 24 November 1925), also spelt Suphayalat, was the last queen of Burma who reigned in Mandalay (1878–1885), born to King Mindon Min and Queen of Alenandaw (lit. 'Middle Palace'; also known as Hsinbyumashin or Lady of the White Elephant). The British corruption of her name was "Soup Plate". She was married to her half-brother, Thibaw, who became the last king of the Konbaung dynasty in 1878, upon Mindon Min's death. She is best known for engineering a massacre of 80 to 100 royal family members, to prevent potential rivals from usurping Thibaw's power, although she had always denied any knowledge of the plot, which may have been hatched by her mother together with some of the ministers, including the chancellor Kinwun Mingyi U Kaung.

King Thibaw was known for his reliance on Supayalat. Although Thibaw was king, many historians say it was Supayalat who actually ruled the country. The bloody coup that brought her and Thibaw to power associated her name with cruelty, brutality and barbarity. As a greatest achievement of Supayalat, she changed the royal tradition of polygamy to monogamy on a Burmese king for the first and the last time in history and never allowed Thibaw to take another woman as a consort. Supayalat executed Daing Khin Khin, the secret concubine of King Thibaw, even though she was pregnant.

In Burmese history, Supayalat is remembered for her ego, cruelty, and excessive pride, serving as the figure held responsible for the kingdom's fall into the hands of the imperialists. She became the embodiment of a Burmese proverb: "A woman can bring ruin to a kingdom [my]" (မိန်းမဖျက် ပြည်ပျက်).

Supayalat was born on 13 December 1859 at the Royal Palace, in Mandalay as Hteik Supayalat, was the second of three daughters of King Mindon and Hsinbyumashin. She was a full-blooded sister of Supayagyi and Supayalay. She received the appanage of Tabayin, Manle [my] and later Myadaung, and was therefore known as the Princess of Myadaung, with the royal title of Sīri Suriya Prabha Ratanā Devī (သီရိသူရိယပြဘရတနာဒေဝိ). She attained the top position among King Mindon's daughters as the firstborn following the establishment of Mandalay Palace.

Hsinbyumashin had planned to arrange a marriage between Thibaw and her eldest daughter, Supayagyi, not Supayalat, but Thibaw declared his love for Supayalat.

The three other queens of Mindon had no children, and Hsinbyumashin became more powerful after the death of the chief queen Setkya Dewi. Thibaw, on the other hand, was the son of a middle-ranking queen, Laungshe Mibaya. He was however learned in the Buddhist scriptures and also educated by the missionary Dr Marks, and became one of Mindon's favourite sons.

In 1878, Thibaw succeeded his father in a succession massacre. Hsinbyumashin, one of Mindon's queens, had grown dominant at the Mandalay court during Mindon's final days. Under the guise that Mindon wanted to bid his children (other princes and princesses) farewell, Hsinbyumashin had all royals of close age (who could potentially be heir to the throne) killed by edict, to ensure that Thibaw and her oldest daughter Hteik Supayagyi would assume the throne.

The ambitious Hsinbyumashin, after putting Thibaw on the throne, offered Supayagyi to be his queen, but during the royal wedding ceremony Supayalat pushed in next to her sister to be anointed queen at the same time, breaking ancient custom. Her sister's marriage was never consummated, and Supayalat was said to have forced monogamy on a Burmese king for the first and the last time in history, even though Thibaw also subsequently married her youngest sister Hteik Supayalay, Princess of Yamethin. Supayalat was 19 and Thibaw 20 when they ascended the lion throne (Thihathana palin). Many historians and media accused Supayalat of also engineering the massacre, but she denied this: